Promethean
Upon arrival of the Forerunner planet, Requiem, both the UNSC Infinity along with the Master Chief, (Sierra 117) and his AI companion Cortana discovered the natives to the planet known as Promethean; Jul 'Mdama;s Covenant faction would also encounter these ancient enemies and ally themselves to their leader, the Didact. The mechanical Prometheans are war machines were created by the Didact after his descent into madness near the end of the Forerunner-Flood war. The Didact viewed these constructs as a novel and effective strategy to fight the Flood without risk of biological infection. They encompass various classes of leader units known as Knights, standard ground forces known as Soldiers, specialized Sentinels known as Watchers, and small, pack-oriented Crawlers designed to overwhelm the enemy from different directions. Knights Promethean Knights are a class of mechanized Forerunner Promethean warriors created by the Didact toward the end of the Forerunner-Flood war to combat the Flood. After the Librarian exiled the Didact on Requiem, several legions of these constructs stationed on the shield world went dormant for the next 100,000 years. The machines—as well as their master—were reawakened in late 2557, when John-117 and the UNSC stumbled upon Requiem. The Promethean Knights are bipedal, fully weaponized mechanical warriors designed to operate and eliminate threats in a wide variety of environments. While the Knights are fully machines, their AI is a result of organic minds transformed into software format via a device called the Composer, unlike the Crawlers or the sentinels which are completely artificial in origin. This extreme measure was intended by the Didact to create an unstoppable army, completely immune to Flood infection, near the end of the Forerunner-Flood war. The Didact's Promethean Warrior-Servants were the first Knights, but these were too few in number to turn the tide. Desperate for greater numbers and still refusing to accept the Halo Array as a final option, the Didact "conscripted" a large population of humans from Omega Halo to expand his army; this genocidal act was the ultimate reason the Librarian imprisoned her husband. Despite housing harvested human and Forerunner essences, the original personalities are no longer in evidence; the Knights are intelligent, but viciously ruthless in behavior and seemingly lacking any form of free will. A Knight's rank is based on a combination of past military service and "popularity amongst their peer group". Even composed children were converted into Promethean Knights. Knights carry a single Promethean Watcher sentinel in the back of their armored carapace, which can be deployed at will for combat support. The Watcher's AI is a low-level ancilla split off from the Knight's essence when the Watcher is deployed. The Watcher can greatly improve the Knight's combat capabilities by raising hardlight shields, reviving fallen Knights, summoning Crawlers, building automated turrets, and flinging back enemy grenades while distracting them with its own weaponry. Promethean Knights utilize a broad arsenal of weapons. For close-quarters combat, they are armed with a hardlight blade on one hand. Each class of Knight has a uniquely shaped blade, totaling six variations amongst them. They also use various Forerunner ranged weapons, such as Scattershots, Suppressors, Lightrifles, Binary Rifles, and Incineration Cannons; their dedicated armament largely depends on their class and role. They frequently employ pulse grenades in combat, generating it from the arm-blade's joint. Some subtypes also make use of autosentries, in addition to the support that they can already summon. Knights are remarkably agile, and in addition to using their limbs for conventional movement they are also capable of translocating over moderate distances, allowing them to either swiftly retreat from the battlefield or to flank their enemies. Although not commonly seen in the field, Knights can also be deployed from warships and are equipped with thruster engines on the sides of their carapace for maneuvering. This capability was used near the end of the Forerunner-Flood war, when Knights were deployed to board and destroy Flood-controlled ships from within. Upon taking critical damage, Knights completely disintegrate, a process that Cortana described as a "data purge." Their bodies erode away from where the fatal shot was received and dissolve into glowing particles. After disintegration, a small ball of swirling light is left behind for a brief period; a Promethean Watcher can use this remnant to recreate and revive the Knight; however, an individual Knight can only be revived in this manner only once. If a Knight is destroyed, revived, and then destroyed again, the Knight's body disintegrates completely, leaving nothing behind. When a Knight is destroyed, it drops a weapon; after revival, it wields a weapon of the same type even if the first weapon was picked up. Solider A Soldier, occasionally referred to as a Promethean Soldier due to the constructs' operational origins, is a class of the armiger developed and primarily utilized by the Forerunner Prometheans. Classified as bipedal combat platforms, Soldiers were deployed during the human-Forerunner wars and the Forerunners' war against the Flood. Unlike the Promethean Knight, which are controlled by the composed essences of formerly living beings, Soldiers are purely artificial intelligence-driven. Soldiers have a distinctly humanoid appearance in comparison to other Promethean constructs and Sentinels; they have one set of arms with small, five-fingered hands. Their main locomotion is provided by a pair of long, thin legs designed for agility and speed. Soldiers are covered in patterns of light and have a fire-like glow inside their heads. In addition, they are capable of slipspace translocation. Unlike the other Promethean units, Promethean Soldiers are also capable of speech. The Soldiers encountered in the modern era are known to taunt their human opponents in English. Their armament are the similar to, but not a complete comparision to the Knights, which consist of: Scattershot, Suppressor, Splinter Turret and Boltshot. They have Splinter Grenades available to them and will use to get distance between themselves and their opponents. Watcher The Promethean Watcher is an advanced Forerunner A.I. that spawn from the carapace of Promethean Knights, and function as support units. Hovering over the battlefield, Watchers provide support fire with their Boltshots, project Hardlight Shields onto Knights, or other Promethean infantry, as well as regenerate destroyed Promethean forces, and redirect enemy ordnance such as grenades back towards the enemy using a gravity displacement beam. The Watcher fulfills a support role, similar to the Huragok. A grenade held in stasis by the gravity displacement beam, will be released when the Watcher is killed or attacked to the point of fleeing the battle and will leave its trajectory according to the physics engine. Crawaler The Promethean Crawler is an advanced Forerunner AI that are quadrupedal in design, and are capable of both close-quarters and long-range combat, having been engineered to ferociously hunt down and eliminate any foreign threats. It is common to encounter Crawlers in substantial numbers, as most travel in large packs and work together in strategic coordination to bring down enemies by overwhelming them from every conceivable angle. Similar to the Covenant's Unggoy, Crawlers act as the cannon fodder of the Prometheans. However, with their advanced agility and use of harassment tactics, they actually fight in a manner more similar to the Covenant's Skirmishers. They are also similar to the Yanme'e, due to their swarming nature and ability to attack from unusual angles. Phaeton The Z-1800 Exoatmospheric Multirole Fighter, also known as the Phaeton, is a Forerunner gunship operated by Prometheans. The Phaeton is a Forerunner Vertical Take-Off and Landing (VTOL) gunship. It has a "boost" ability which lets it move rapidly from side to side or forward and backward. The gunship is armed with both a Hard light turret underneath and twin missile launchers mounted under each wing that can fire four missiles at a time.